Fiber Network Layers and Flexible Penetration Resistant Articles Comprising Same

ABSTRACT

The present invention is directed to a fiber network layer for use in penetration resistant articles having a first plurality of yarns and a second plurality of yarns, each of the first and second yarns arranged in a first direction parallel or substantially parallel to the other first and second yarns and a third plurality of yarns, each of the third yarns arranged in a second direction parallel or substantially parallel to the other third yarns; the second direction transverse to the first direction. The third yarns and either the first yarns or the second yarns are made of a first polymer. Each of the first, second and third yarns having a tenacity of at least 15 g/dtex. The layers are such that either (i) the second yarns are made of a second polymer which is different than the first polymer, or (ii) the first yarns have a different average linear density than the average linear density of the second yarns, or (iii) the first and second yarns comprise multifilament yarns with filaments and the filaments of the first yarns have an average linear density different from the filaments in the second yarns, or (iv) combinations thereof.

RELATED APPLICATIONS

This application claims benefit of U.S. Provisional Application No.60/707,200, filed Aug. 10, 2005, and U.S. Provisional Application No.60/720,898, filed Sep. 27, 2005, the disclosures of which areincorporated herein by reference in their entirety.

FIELD OF THE INVENTION

The present invention relates to a fiber network layer for use inpenetration resistant articles and to articles that contain one or moresuch layers.

BACKGROUND OF THE INVENTION

Reports indicate that antiballistic vests made of 100%poly(p-phenylene-2,6-benzobisoxazole) fabrics (PBO fabrics) can exhibithigher ballistic performance than conventional fabrics. The PBO fabrics,however, are very expensive and are of limited use for some lifeprotection applications.

Various fabric constructions are know for anti-ballistic materials. Itis know, for example, to use different layers where a first layer isconstructed of fibers of a first polymer and a second layer isconstructed of fibers of a different polymer.

It also known that fibers of two polymer can be used in a single layer.Canadian Patent Application CA1034842, for example, teaches multipleweave protective fabrics woven in an asymmetrical weave using warp andweft fibers of dissimilar properties. Another published application,Canadian Patent Application CA2313995, teaches a weave where twoadjacent fibers in both the warp and weft are of different materials.

U.S. Pat. No. 6,155,306 teaches multifilament bulletproof fabrics thatcan have a warp having polyethylene fibers and a weft comprising aramidfibers. U.S. Pat. No. 6,610,619 teaches a multilayer crossplied fabricswith a first set of threads traverse to a second set of threads wherethe ratio of linear density of the first set of threads to the secondset of threads is greater than 4.2. U.S. Pat. No. 5,180,880 teaches asoft vest having a combination of dissimilar materials where the warpyarns are aramid and the fill yarn is a thermoplastic material. EuropeanPatent Application EP 310199(A1) teaches bulletproof woven fabrics withdifferent materials in the warp and fill directions. U.S. Pat. No.5,187,003 discloses a woven antiballistic fabric where fibers in thefill direction have a greater elongation to break than the fibers in thewarp direction.

Despite these advances, there is a need for lighter weight, higherperformance life protection body armors.

SUMMARY OF THE INVENTION

The present invention is directed to a fiber network layer for use inpenetration resistant articles, comprises:

-   -   a first plurality of yarns and a second plurality of yarns, each        of the first and second yarns arranged in a first direction        parallel or substantially parallel to the other first and second        yarns; and    -   a third plurality of yarns, each of the third yarns arranged in        a second direction parallel or substantially parallel to the        other third yarns, the second direction transverse to the first        direction, the third yarns and either the first yarns or the        second yarns made of a first polymer;

wherein each of the first, second and third yarns having a tenacity ofat least 15 g/dtex (preferably from 20 to 45 g/dtex in someembodiments), and

wherein (i) the second yarns are made of a second polymer which isdifferent than the first polymer, or (ii) the first yarns have adifferent average linear density than the average linear density of thesecond yarns, or (iii) the first and second yarns comprise multifilamentyarns with filaments and the filaments of the first yarns have anaverage linear density different from the filaments in the second yarns,or (iv) combinations thereof.

In some preferred embodiments, the fiber network layer further comprisesa fourth plurality of yarns, each of the fourth yarns arranged in thesecond direction parallel or substantially parallel to the third yarnswherein (i) the fourth yarns are made of the second polymer or a thirdpolymer, or (ii) the third yarns have a different average linear densitythan the average linear density of the fourth yarns, or (iii) the thirdand fourth yarns comprise multifilament yarns with filaments and thefilaments of the third yarns have an average linear density differentfrom the filaments in the fourth yarns, or (iv) combinations thereof.

In certain embodiments, the first yarns comprise at least 35%[preferably 40 to 60% in some embodiments] of the total number of yarnsin the first direction, and

the second yarns comprise at least 35% [preferably 40 to 60% in someembodiments] of the total number of yarns in the first direction.

In some embodiments, all fibers in the second direction are of the thirdplurality of yarns.

In some fiber networks, the fiber network layer has an areal density ofno more than 10 kg/m². In some embodiments, the areal density ispreferably 2 to 8 kg/m².

In certain aspects of the invention, each of the first, second, andthird yarns have an elongation at break of at least 2% (preferably from2.5% to 10% in some embodiments) and a modulus of elasticity of at least150 grams per dtex (preferably from 250 to 2000 in some embodiments).

Certain layers are such that each of the first, second, and third yarnsyearns have a tenacity of at least 15 grams per denier (preferably atleast 20 grams per denier in some embodiments). In other embodiments,the fiber network layer has at least one of the first, second, and thirdyarns have a tenacity of at least 30 grams per denier. In someembodiments, the tenacity is preferably at least 35 grams per denier.

Some layers have at least one of the first, second, and third yarnsyearns have a tenacity of least 30 grams per denier and density of atleast 1.6 grams per cubic centimeter.

In some embodiments, the second yarns are made of a second polymer whichis different than the first polymer.

In certain embodiments, the first yarns have a different average lineardensity than the average linear density of the second yarns. In someembodiments, the first and second yarns comprise multifilament yarnswith filaments and the filaments of the first yarns have an averagelinear density different from the filaments in the second yarns.

In some aspects, the invention concerns a fiber network layer where thefirst and third yarns are made of the first polymer and havesubstantially the same average linear density, and the filaments of thefirst and third yarns have substantially the same average lineardensity.

In some layers, each of the first, second, and third yarns have a lineardensity of 100 to 5000 decitex. In some embodiments, the linear densityis preferably 220 to 3300 decitex. In certain layers, the first, second,and third yarns have a linear density of 0.1 to 10 decitex. In certainembodiments, the yarns are preferably 0.2 to 5.5 decitex.

Some layers of the invention comprise filaments of the first, second andthird yarns are continuous filaments, staple fibers, or mixtures ofboth.

In some embodiments, the first and second yarns arranged in analternating sequence.

The first and second polymers, in some embodiments, are selected fromthe group consisting of polyamide, polyolefin, polybenzoxazole,polybenzothiazole,poly{2,6-diimidazo[4,5-b4′,5′-e]pyridinylene-1,4(2,5-dihydroxy)phenylene},polyareneazoles, polypyridazoles, polypyridobisimidazoles and mixturesthereof. In certain embodiments, the first polymer is poly (p-phenyleneterephtahlamide).

Some layer of the invention are such that the first yarns, the secondyarns, and the third yarns are woven, nonwoven, or a unidirectionalarray stacked othogonally on a unidirectional array.

The invention also relates to a flexible penetration resistant articlecomprising a plurality of fiber network layers as described herein. Someflexible penetration resistant articles have an areal density of 2 to 12kg/m². Certain articles have at least one layer of fabric layers beingimpregnated with a polymeric matrix comprising a thermoset resin, athermoplastic resin, or mixtures thereof.

In some embodiments, the invention also concerns a method of weavingfiber networks. In one embodiments, A method of making a fiber networklayer comprising:

weaving a first plurality of yarns and a second plurality of yarns, eachof the first and second yarns in a first direction parallel orsubstantially parallel to the other first and second yarns;

with a third plurality of yarns, each of the third yarns arranged in asecond direction parallel or substantially parallel to the other thirdyarns, the second direction transverse to the first direction, the thirdyarns and either the first yarns or the second yarns made of a firstpolymer;

wherein:

-   -   each of the first, second and third yarns having a tenacity of        at least 15 g/dtex, and    -   (i) the second yarns are made of a second polymer which is        different than the first polymer, or (ii) the first yarns have a        different average linear density than the average linear density        of the second yarns, or (iii) the first and second yarns        comprise multifilament yarns with filaments and the filaments of        the first yarns have an average linear density different from        the filaments in the second yarns, or (iv) combinations thereof.

in certain embodiments, the method further comprises weaving a fourthplurality of yarns, each of the fourth yarns arranged in the seconddirection parallel or substantially parallel to the third yarns,

wherein (i) the fourth yarns are made of the second polymer or a thirdpolymer, or (ii) the third yarns have a different average linear densitythan the average linear density of the fourth yarns, or (iii) the thirdand fourth yarns comprise multifilament yarns with filaments and thefilaments of the third yarns have an average linear density differentfrom the filaments in the fourth yarns, or (iv) combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a weave having a first and a second yarn in a firstdirection and a third yarn in a second direction.

FIG. 2 shows a weave having a first and a second yarn in a firstdirection and a third and fourth yarn in a second direction.

DETAILED DESCRIPTION

The present invention may be understood more readily by reference to thefollowing detailed description of illustrative and preferred embodimentsthat form a part of this disclosure. It is to be understood that thescope of the claims is not limited to the specific devices, methods,conditions or parameters described and/or shown herein, and that theterminology used herein is for the purpose of describing particularembodiments by way of example only and is not intended to be limiting ofthe claimed invention. Also, as used in the specification including theappended claims, the singular forms “a,” “an,” and “the” include theplural, and reference to a particular numerical value includes at leastthat particular value, unless the context clearly dictates otherwise.When a range of values is expressed, another embodiment includes fromthe one particular value and/or to the other particular value.Similarly, when values are expressed as approximations, by use of theantecedent “about,” it will be understood that the particular valueforms another embodiment. All ranges are inclusive and combinable.

Penetration resistant composites and articles of the present inventionpreferably include a plurality of fibrous layers that are made frompolymer fibers.

For purposes herein, the term “fiber” is defined as a relativelyflexible, macroscopically homogeneous body having a high ratio of lengthto width across its cross-sectional area perpendicular to its length.The fiber cross section can be any shape, but is typically round. Thefibers can be present in uncoated, or coated, or otherwise pretreated(for example, pre-stretched or heat-treated) form. Herein, the term“filament” is used interchangeably with the term “fiber.”

As herein defined, “yarn” refers to a continuous length of two or morefibers, wherein fiber is as defined herein.

For purposes herein, “fabric” refers to any woven, knitted, or non-wovenstructure. By “woven” is meant any fabric weave, such as, plain weave,crowfoot weave, basket weave, satin weave, twill weave, and the like. By“knitted” is meant a structure produced by interlooping or intermeshingone or more ends, fibers or multifilament yarns. By “non-woven” is meanta network of fibers, including unidirectional fibers, felt, and thelike.

The fibrous layers can take on numerous configurations, including, butnot limited to, knitted or woven fabrics or non-woven structures. Bynon-woven is meant a network of fibers, including unidirectional (ifcontained within a matrix resin), felt, and the like. By woven is meantany fabric weave, such as, plain weave, crowfoot weave, basket weave,satin weave, twill weave, and the like. Plain weave is believed to bethe most common weave used in the trade.

In some preferred embodiments, the fabric is a made by weaving aplurality of yarns.

The areal density of the fabric layer is determined by measuring theweight of each single layer of selected size, e.g., 10 cm×10 cm. Theareal density of the composite structure is determined by the sum of theareal densities of the individual layers.

Denier is determined according to ASTM D 1577 and is the linear densityof a fiber as expressed as weight in grams of 9000 meters of fiber.

Tenacity is determined according to ASTM D 885 and is the maximum orbreaking stress of a fiber as expressed as grams per denier.

A wide variety of suitable thermoset and thermoplastic resins andmixtures thereof are well known in the prior art and can be used as thematrix material. For example, thermoplastic resins can comprise one ormore polyurethane, polyimide, polyethylene, polyester, polyetheretherketone, polyamide, polycarbonate, and the like. Thermoset resinscan be one or more epoxy-based resin, polyester-based resin,phenolic-based resin, and the like, preferably a polyvinylbutyralphenolic resin. Mixtures can be any combination of the thermoplasticresins and the thermoset resins.

A representative list of fibers suitable for this invention includepolyamide fibers, polyolefin fibers, polybenzoxazole fibers,polybenzothiazole fibers,poly{2,6-diimidazo[4,5-b4′,5′-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}(PIPD) fiber, or mixtures thereof. Preferably, the fibers are made ofpoly{2,6-diimidazo[4,5-b4′,5′-e]pyridinylene-1,4(2,5-dihydroxy)phenylene}(PIPD) fiber.

When the polymer is polyamide, aramid is preferred. By “aramid” is meanta polyamide wherein at least 85% of the amide (—CO—NH—) linkages areattached directly to two aromatic rings. Suitable aramid fibers aredescribed in Man-Made Fibers—Science and Technology, Volume 2, Sectiontitled Fiber-Forming Aromatic Polyamides, page 297, W. Black et al.,Interscience Publishers, 1968. Aramid fibers are, also, disclosed inU.S. Pat. Nos. 4,172,938; 3,869,429; 3,819,587; 3,673,143; 3,354,127;and 3,094,511. Additives can be used with the aramid and it has beenfound that up to as much as 10 percent, by weight, of other polymericmaterial can be blended with the aramid or that copolymers can be usedhaving as much as 10 percent of other diamine substituted for thediamine of the aramid or as much as 10 percent of other diacid chloridesubstituted for the diacid chloride or the aramid.

The preferred aramid is a para-aramid and poly(p-phenyleneterephthalamide) (PPD-T) is the preferred para-aramid. By PPD-T is meantthe homopolymer resulting from approximately mole-for-molepolymerization of p-phenylene diamine and terephthaloyl chloride and,also, copolymers resulting from incorporation of small amounts of otherdiamines with the p-phenylene diamine and of small amounts of otherdiacid chlorides with the terephthaloyl chloride. As a general rule,other diamines and other diacid chlorides can be used in amounts up toas much as about 10 mole percent of the p-phenylene diamine or theterephthaloyl chloride, or perhaps slightly higher, provided only thatthe other diamines and diacid chlorides have no reactive groups whichinterfere with the polymerization reaction. PPD-T, also, meanscopolymers resulting from incorporation of other aromatic diamines andother aromatic diacid chlorides such as, for example, 2,6-naphthaloylchloride or chloro- or dichloroterephthaloyl chloride or3,4′-diaminodiphenylether.

When the polymer is polyolefin, polyethylene or polypropylene arepreferred. By polyethylene is meant a predominantly linear polyethylenematerial of preferably more than one million molecular weight that maycontain minor amounts of chain branching or comonomers not exceeding 5modifying units per 100 main chain carbon atoms, and that may alsocontain admixed therewith not more than about 50 weight percent of oneor more polymeric additives such as alkene-1-polymers, in particular lowdensity polyethylene, propylene, and the like, or low molecular weightadditives such as anti-oxidants, lubricants, ultra-violet screeningagents, colorants and the like which are commonly incorporated. Such iscommonly known as extended chain polyethylene (ECPE). Similarly,polypropylene is a predominantly linear polypropylene material ofpreferably more than one million molecular weight. High molecular weightlinear polyolefin fibers are commercially available. Preparation ofpolyolefin fibers is discussed in U.S. Pat. No. 4,457,985.

Polyareneazole polymer may be made by reacting a mix of dry ingredientswith a polyphosphoric acid (PPA) solution. The dry ingredients maycomprise azole-forming monomers and metal powders. Accurately weighedbatches of these dry ingredients can be obtained through employment ofat least some of the preferred embodiments of the present invention.

Exemplary azole-forming monomers include 2,5-dimercapto-p-phenylenediamine, terephthalic acid, bis-(4-benzoic acid), oxy-bis-(4-benzoicacid), 2,5-dihydroxyterephthalic acid, isophthalic acid,2,5-pyridodicarboxylic acid, 2,6-napthalenedicarboxylic acid,2,6-quinolinedicarboxylic acid,2,6-bis(4-carboxyphenyl)pyridobisimidazole, 2,3,5,6-tetraminopyridine,4,6-diaminoresorcinol, 2,5-diaminohydroquinone,1,4-diamino-2,5-dithiobenzene, or any combination thereof. Preferably,the azole forming monomers include 2,3,5,6-tetraminopyridine and2,5-dihydroxyterephthalic acid. In certain embodiments, it is preferredthat that the azole-forming monomers are phosphorylated. Preferably,phosphorylated azole-forming monomers are polymerized in the presence ofpolyphosphoric acid and a metal catalyst.

Metal powders can be employed to help build the molecular weight of thefinal polymer. The metal powders typically include iron powder, tinpowder, vanadium powder, chromium powder, and any combination thereof.

The azole-forming monomers and metal powders are mixed and then themixture is reacted with polyphosphoric acid to form a polyareneazolepolymer solution. Additional polyphosphoric acid can be added to thepolymer solution if desired. The polymer solution is typically extrudedor spun through a die or spinneret to prepare or spin the filament.

Polybenzoxazole (PBO) and polybenzothiazole (PBZ) two suitable polymers.These polymers are described in PCT Application No. WO 93/20400.Polybenzoxazole and polybenzothiazole are preferably made up ofrepetitive units of the following structures:

While the aromatic groups shown joined to the nitrogen atoms may beheterocyclic, they are preferably carbocyclic; and while they may befused or unfused polycyclic systems, they are preferably singlesix-membered rings. While the group shown in the main chain of thebis-azoles is the preferred para-phenylene group, that group may bereplaced by any divalent organic group which doesn't interfere withpreparation of the polymer, or no group at all. For example, that groupmay be aliphatic up to twelve carbon atoms, tolylene, biphenylene,bis-phenylene ether, and the like.

The polybenzoxazole and polybenzothiazole used to make fibers of thisinvention should have at least 25 and preferably at least 100 repetitiveunits. Preparation of the polymers and spinning of those polymers isdisclosed in the aforementioned PCT application WO 93/20400.

M5 fiber is suitable for use in the instant invention. This fiber isbased on poly [diimidazo pyridinylene (dihydroxy)phenylene]. M5 fibersare known to have an average modulus of about 310 GPa and an averagetenacities of up to about 5.8 GPa. M5 fibers have been described byBrew, et al., Composites Science and Technology 1999, 59, 1109; Van derJagt and Beukers, Polymer 1999, 40, 1035; Sikkema, Polymer 1998, 39,5981; Klop and Lammers, Polymer, 1998, 39, 5987; Hageman, et al.,Polymer 1999, 40, 1313.

A laminated layer is defined as a network of fibers impregnated with apolymeric matrix comprising a thermoset or thermoplastic resin, ormixtures thereof. Each layer adds to the thickness and weight of thecomposite structure, thereby reducing its flexibility, wearability andcomfort. Therefore, the numbers of layers have been selected such thatthe total composite structure is designed and used to protect against aspecific threat.

The layers can be held together or joined in any manner, such as, bybeing sewn together or they can be stacked together and held, forexample, in a fabric envelope or carrier. The layers which form thesections can be separately stacked and joined, or all of the pluralityof layers can be stacked and joined as a single unit.

The layers can also be held together by the polymeric matrix comprisinga thermoset or thermoplastic resin, or mixtures thereof. A wide varietyof suitable thermoset and thermoplastic resins and mixtures thereof arewell known in the prior art and can be used as the matrix material. Forexample, thermoplastic resins can comprise one or more polyurethane,polyimide, polyethylene, polyester, polyether etherketone, polyamide,polycarbonate, and the like. Thermoset resins can be one or moreepoxy-based resin, polyester-based resin, phenolic-based resin, and thelike, preferably a polyvinlybutyral phenolic resin. Mixtures can be anycombination of the thermoplastic resins and the thermoset resins. Theproportion of the matrix material in each layer is from about 10% toabout 80% by weight of the layer preferably 20% to 60% by weight of thelayer.

Various amounts of ultraviolet absorbers or sabilizers can be added tothe fiber or laminated layers to absorb harmful ultraviolet radiationand dissipate it as thermal energy. UV absorbers act by shielding thefiber or laminated layers from the UV light, while the UV stabilizersact by scavenging the radical intermediates formed in thephoto-oxidation process to enhance the service life of fiber orlaminated layers when exposed to UV light. Examples of UV absorbersinclude benzophenone or the benzotriazole of Ciba Specialty Chemicals.

In FIG. 1, a weave having a first and a second yarn in a first directionand a third yarn in a second direction is depicted. In thisillustration, the first and second yarns are substantially parallel andtraverse to the direction of the third yarn.

Test Methods

The following test methods were used in the following Examples.

Linear Density. The linear density of a yarn or fiber is determined byweighing a known length of the yarn or fiber based on the proceduresdescribed in ASTM D1907-97 and D885-98. Decitex or “dtex” is defined asthe weight, in grams, of 10,000 meters of the yarn or fiber.

Areal Density. The areal density of the fabric layer is determined bymeasuring the weight of each single layer of selected size, e.g., 10cm×10 cm. The areal density of the composite structure is determined bythe sum of the areal densities of the individual layers.

Ballistic Resistance Penetration. The V50 Ballistic tests of themulti-layer panels were conducted in accordance with NIJStandard—0101.04 “Ballistic Resistance of Personal Body Armor”, issuedin September 2000. this test only discloses use of 9 mm but we used sametest with 9 mm and also 0.357 bullets

EXAMPLES

This invention will now be illustrated by the following specificexamples. All parts and percentages are by weight unless otherwiseindicated. Examples prepared according to the process or processes ofthe current invention are indicated by numerical values. Control orComparative Examples are indicated by letters.

Preparation and Testing of Examples

In the following examples, a plurality layers of woven fabric withvarious combinations of aramid and polybenzoxazole (PBO) yarns in bothwarp and fill directions were prepared. The aramid yarn was sold by E.I.du Pont de Nemours and Company under the trademark KEVLAR®. The aramidwas poly(p-phenylene terephthalamide). The polybenzoxazole (PBO) yarnwas sold by Toyobo Co., Ltd., under the trademark ZYLON®. Composites ofa plurality of fabric layers were tested for ballistic resistancepenetration. Ballistic panels of 16 in² (40.6 cm²) were constructed foreach test, wherein all of the fabric layers were sewn around the edgesand were additionally sewn diagonally with cross-stitches. Severaldifferent fabrics made from yarns of various materials and differentlinear density of yarns were tested at various areal densities between3.7 and 6.0 kg/m².

Example 1

In Example 1, forty-four layers of fabric were woven from 440 dtexKEVLAR® 129 and 550 dtex ZYLON® yarns arranged in an alternate sequence,i.e., a KEVLAR® yarn/a ZYLON® yarn/a KEVLAR® yarn/a ZYLON® yarn, in boththe warp and fill directions in a plain weave at 10.2 ends percentimeter and an areal density of about 4.7 kg/m2.

Comparative Example A

In Comparative Example A, forty-four layers of fabric were made with 550dtex ZYLON® yarn in the warp direction at 9.8 ends per centimeter and440 dtex KEVLAR® 129 yarn in the fill direction at 11.0 ends percentimeter in a plain weave, and an areal density of about 4.7 kg/m².

Comparative Example B

In Comparative Example B, forty-four layers of fabric were made with 440dtex KEVLAR® 129 yarn in the warp direction at 11.0 ends per centimeterand 550 dtex ZYLON® yarn in the fill direction at 9.8 ends percentimeter in a plain weave, and an areal density of about 4.7 kg/m².

The layers of fabrics in Example 1 and Comparative Examples A and B weretested for ballistic V50 against 9 mm and 0.357 mag bullets. Theballistic test results, shown in Table 1, indicate the V50 results forthe articles of this invention as shown in Example 1 were significantlygreater than the V50 of the article of Comparative Examples A and B. Insummary, the articles of the invention showed an improvement inballistic V50 of from about 3% to 8% compared to the article ofComparative Examples A and B.

TABLE 1 V50 (9 mm) improvement V50 (.357 mag) improvement Example(m/sec) of Ex 1 (m/sec) of Ex 1 1 540 536 A 522 3.5% 495 8.3% B 525 2.9%516 3.9%

Example 2

In Example 2, thirty-five layers of fabric were woven from 440 dtexKEVLAR® 129 and 550 dtex ZYLON® yarns arranged in an alternate sequencein both the warp and fill directions in a plain weave at 10.2 ends percentimeter and an areal density of about 3.7 kg/m².

Comparative Example C

In Comparative Example C, thirty-five layers of fabric were made with550 dtex ZYLON® yarn in the warp direction at 9.8 ends per centimeterand 440 dtex KEVLAR® 129 yarn in the fill direction at 11.0 ends percentimeter in a plain weave, and an areal density of about 3.7 kg/m².

Comparative Example D

In Comparative Example D, thirty-five layers of fabric were made with440 dtex KEVLAR® 129 yarn in the warp direction at 11.0 ends percentimeter and 550 dtex ZYLON® yarn in the fill direction at 9.8 endsper centimeter in a plain weave, and an areal density of about 3.7kg/m².

The layers of fabrics in Example 2 and Comparative Examples C and D weretested for ballistic V50 against 9 mm and 0.357 mag bullets. Theballistic test results, shown in Table 2, indicate the V50 results forthe articles of this invention as shown in Examples 2 were significantlygreater than the V50 of the article of Comparative Examples C and D.

TABLE 2 V50 (9 mm) Improvement V50 (.357 mag) Improvement Example(m/sec) of Ex 2 (m/sec) of Ex 2 2 500 508 C 496 0.1% 472 7.6% D 469 6.6%470 8.1%

Example 3

In Example 3, thirty-six layers of fabric were woven from 1110 dtexKEVLAR® 129 and 1110 dtex ZYLON® yarns arranged in an alternate sequencein both the warp and fill directions in a plain weave at 7.5 ends percentimeter and an areal density of about 6.0 kg/m².

Comparative Example E

In Comparative Example E, thirty-six layers of fabric were made with1110 dtex ZYLON® yarn in the warp direction at 7.5 ends per centimeterand 1110 dtex KEVLAR® 129 yarn in the fill direction at 7.5 ends percentimeter in a plain weave, and an areal density of about 6.0 kg/m².

The layers of fabrics in Example 3 and Comparative Example E were testedfor ballistic V50 against 9 mm and 0.357 mag bullets. The ballistic testresults, shown in Table 3, indicate the V50 results for the articles ofthis invention, as shown in Example 3, were significantly greater thanthe V50 of the article of Comparative Example E.

TABLE 3 V50 (9 mm) Improvement V50 (.357 mag) Improvement Example(m/sec) of Ex 3 (m/sec) of Ex 3 3 594 564 E 564 5.3% 558 1.1%

Example 4

In Example 4, the structures of examples 1-3 may be replicated with afiber selected from polyareneazoles, polypyridazoles,polypyridobisimidazoles or any combination thereof in place of theKEVLAR® fiber.

Example 5

In Example 5, the structures of Examples 1-3 may be replicated with afiber selected from polyareneazoles, polypyridazoles,polypyridobisimidazoles or any combination thereof in place of theZYLON® fiber.

While the present invention has been described in connection with thepreferred embodiments of the figures, it is to be understood that othersimilar embodiments may be used or modifications and additions may bemade to the described embodiment for performing the same function of thepresent invention without deviating therefrom. Therefore, the presentinvention should not be limited to any single embodiment, but ratherconstrued in breadth and scope in accordance with the recitation of theappended claims.

All patents and publications disclosed herein are incorporated byreference in their entirety.

1. A fiber network layer for use in penetration resistant articles,comprising: a first plurality of yarns and a second plurality of yarns,each of the first and second yarns arranged in a first directionparallel or substantially parallel to the other first and second yarns;a third plurality of yarns, each of the third yarns arranged in a seconddirection parallel or substantially parallel to the other third yarns,the second direction transverse to the first direction, the third yarnsand either the first yarns or the second yarns made of a first polymer;and each of the first, second and third yarns having a tenacity of atleast 15 g/dtex; wherein (i) the second yarns are made of a secondpolymer which is different than the first polymer, or (ii) the firstyarns have a different average linear density than the average lineardensity of the second yarns, or (iii) the first and second yarnscomprise multifilament yarns with filaments and the filaments of thefirst yarns have an average linear density different from the filamentsin the second yarns, or (iv) combinations thereof.
 2. The fiber networklayer of claim 1, further comprising: a fourth plurality of yarns, eachof the fourth yarns arranged in the second direction parallel orsubstantially parallel to the third yarns, wherein (i) the fourth yarnsare made of the second polymer or a third polymer, or (ii) the thirdyarns have a different average linear density than the average lineardensity of the fourth yarns, or (iii) the third and fourth yarnscomprise multifilament yarns with filaments and the filaments of thethird yarns have an average linear density different from the filamentsin the fourth yarns, or (iv) combinations thereof.
 3. The fiber networklayer of claim 1, wherein: the first yarns comprise at least 35% of thetotal number of yarns in the first direction, and the second yarnscomprise at least 35% of the total number of yarns in the firstdirection.
 4. The fiber network layer of claim 2, wherein: the thirdyarns comprise at least 25% of the total number of yarns in the seconddirection, and the fourth yarns comprise at least 25% of the totalnumber of yarns in the second direction.
 5. The fiber network layer ofclaim 1, wherein the fiber network layer has an areal density of no morethan 10 kg/m².
 6. The fiber network layer of claim 2, wherein each ofthe first, second, third and fourth yarns have an elongation at break ofat least 2% and a modulus of elasticity of at least 150 grams per dtex.7. The fiber network layer of claim 1, wherein the second yarns are madeof a second polymer which is different than the first polymer.
 8. Thefiber network layer of claim 1, wherein the first yarns have a differentaverage linear density than the average linear density of the secondyarns.
 9. The fiber network layer of claim 1, wherein the first andsecond yarns comprise multifilament yarns with filaments and thefilaments of the first yarns have an average linear density differentfrom the filaments in the second yarns.
 10. The fiber network layer ofclaim 1, wherein: the first and third yarns are made of the firstpolymer, have the same average linear density, and the filaments of thefirst and third yarns have the same average linear density, and thesecond and fourth yarns are made of the second polymer, have the sameaverage linear density, and the filaments of the second and fourth yarnshave the same average linear density.
 11. The fiber network layers ofclaim 2, wherein the filaments of the first, second, third and fourthyarns have a linear density of 0.1 to 10 decitex.
 12. The fiber networklayer of claim 1, wherein the first and second yarns arranged in analternating sequence.
 13. The fiber network layer of claim 2, whereinthe third and fourth yarns arranged in an alternating sequence.
 14. Thefiber network layer of claim 1, wherein the first and second polymersare selected from the group consisting of polyamide, polyolefin,polybenzoxazole, polybenzothiazole,poly{2,6-diimidazo[4,5-b4′,5′-e]pyridinylene-1,4(2,5-dihydroxy)phenylene},polyareneazoles, polypyridazoles, polypyridobisimidazoles and mixturesthereof.
 15. A flexible penetration resistant article comprising aplurality of fiber network layers of claim
 1. 16. The flexiblepenetration resistant article of claim 15, wherein the article has anareal density of 2 to 12 kg/m².
 17. A flexible ballistic resistantarticle, comprising a plurality of layers of fabric having two differenttypes of yarns arranged in an alternating sequence in both warp and filldirections of the fabric.
 18. The flexible ballistic resistant articleof claim 17 wherein at least one layer of said fabric layers beingimpregnated with a polymeric matrix comprising a thermoset resin, athermoplastic resin, or mixtures thereof.
 19. A method of forming afiber network comprising: weaving a first plurality of yarns and asecond plurality of yarns, each of the first and second yarns arrangedin a first direction parallel or substantially parallel to the otherfirst and second yarns; with a third plurality of yarns, each of thethird yarns arranged in a second direction parallel or substantiallyparallel to the other third yarns, the second direction transverse tothe first direction, the third yarns and either the first yarns or thesecond yarns made of a first polymer; and each of the first, second andthird yarns having a tenacity of at least 15 g/dtex; wherein (i) thesecond yarns are made of a second polymer which is different than thefirst polymer, or (ii) the first yarns have a different average lineardensity than the average linear density of the second yarns, or (iii)the first and second yarns comprise multifilament yarns with filamentsand the filaments of the first yarns have an average linear densitydifferent from the filaments in the second yarns, or (iv) combinationsthereof.
 20. The method of claim 19 further comprising: weaving a fourthplurality of yarns, each of the fourth yarns arranged in the seconddirection parallel or substantially parallel to the third yarns, wherein(i) the fourth yarns are made of the second polymer or a third polymer,or (ii) the third yarns have a different average linear density than theaverage linear density of the fourth yarns, or (iii) the third andfourth yarns comprise multifilament yarns with filaments and thefilaments of the third yarns have an average linear density differentfrom the filaments in the fourth yarns, or (iv) combinations thereof.